Enzymes
Cellular Energy
Respiration
Photosynthesis
Resp and Photo pt 2
100
What is the role of an enzyme in a chemical reaction?
It lowers the activation energy needed for the reaction to proceed.
100
What does ATP stand for?
Adenosine triphosphate.
100
Where in the cell does glycolysis occur?
In the cytoplasm.
100
What organelle is the site of photosynthesis?
The chloroplast.
100
Which molecule is both a product of photosynthesis and a reactant in cellular respiration?
Glucose.
200
What happens to an enzyme's activity if the temperature or pH is too far from its optimum?
The enzyme may denature, losing its functional shape and activity.
200
Which bond in ATP is broken to release energy?
he bond between the second and third phosphate groups.
200
What are the products of glycolysis?
2 pyruvate, 2 ATP (net), and 2 NADH.
200
What are the two stages of photosynthesis?
The light-dependent reactions and the Calvin cycle (light-independent reactions).
200
How are mitochondria and chloroplasts structurally similar?
Both have a double membrane and internal membrane systems; both generate ATP using chemiosmosis.
300
Describe how competitive inhibition differs from noncompetitive inhibition.
Competitive inhibitors bind to the active site; noncompetitive inhibitors bind elsewhere, changing the enzyme's shape.
300
Describe how ATP is regenerated in the cell.
By adding a phosphate group to ADP during cellular respiration, especially in oxidative phosphorylation.
300
What is the main function of the electron transport chain in cellular respiration?
To create a proton gradient used to make ATP via chemiosmosis.
300
What is the role of water in the light-dependent reactions?
It is split to provide electrons, protons, and O₂.
300
ompare the role of NADH in cellular respiration to the role of NADPH in photosynthesis.
NADH carries electrons to the mitochondrial electron transport chain; NADPH provides electrons for carbon fixation in the Calvin cycle.
400
A mutation changes an enzyme's active site. Predict and explain the effect on the enzyme’s function.
The enzyme may lose its ability to bind the substrate effectively, reducing or eliminating its catalytic activity.
400
A chemical reaction in a cell has a ΔG of +3.5 kcal/mol. ATP hydrolysis has a ΔG of -7.3 kcal/mol. Explain how ATP can be used to make this reaction occur in the cell.
The cell can couple the endergonic reaction (+3.5 kcal/mol) with the exergonic ATP hydrolysis (-7.3 kcal/mol). The combined ΔG is negative (-3.8 kcal/mol), making the overall reaction spontaneous. This is how cells use ATP to power reactions that wouldn’t occur on their own.
400
Why is oxygen required for aerobic respiration?
It acts as the final electron acceptor in the electron transport chain.
400
Where do the Calvin cycle reactions occur, and what is their main product?
In the stroma; they produce G3P, a 3-carbon sugar.
400
f a plant is exposed to a toxin that blocks ATP synthase in the chloroplast, what will happen to the Calvin cycle and why?
The Calvin cycle will stop because ATP is required to convert 3-PGA to G3P.
500
The graph below shows the rate of an enzyme-catalyzed reaction at various temperatures. Analyze the graph and explain the observed trends. Then, draw a model of the enzyme's active site and indicate how its structure might change beyond the enzyme’s optimal temperature.
The graph shows that enzyme activity increases with temperature up to the enzyme’s optimal temperature (e.g., 37°C), where molecular collisions are more frequent. Beyond this point, the rate sharply declines due to denaturation. The heat disrupts hydrogen bonds and other interactions maintaining the enzyme’s tertiary structure, deforming the active site.
500
Many enzymes require ATP to function, even if they aren’t making ATP. Explain how ATP helps these enzymes drive chemical changes, using the idea of coupling.
ATP helps enzymes by transferring a phosphate group to a reactant or the enzyme itself. This added phosphate raises the energy of the molecule, making it more likely to react. This is an example of energy coupling—using ATP’s energy to make other reactions happen.
500
Compare the ATP yield of aerobic vs. anaerobic respiration.
Aerobic respiration yields about 30–32 ATP per glucose; anaerobic yields only 2 ATP per glucose.
500
Explain how the proton gradient is established in the chloroplast and how it drives ATP production.
Protons are pumped into the thylakoid lumen during the electron transport chain; they flow back through ATP synthase to generate ATP.
500
Explain how the processes of photosynthesis and cellular respiration form a cycle of matter and energy in a plant cell. Why is it incorrect to say that one process simply “reverses” the other?
Photosynthesis converts light energy into chemical energy by fixing carbon dioxide into glucose and releasing oxygen. Cellular respiration breaks down glucose in the presence of oxygen to produce ATP, releasing carbon dioxide and water. While the overall reactants and products appear reversed, the processes occur in different organelles, use different energy sources (light vs. chemical), and involve different pathways. Photosynthesis stores energy; respiration releases it. They are complementary but not exact opposites.